I have a Pure Energy 68/3000 carbonfibre tank but the o-ring keeps getting caught on the bottom of the nipple causing it to leak. It has done this from day 1 and is very annoying. I tried another nipple from local store but it was a different brand and the pin didn't move when installed (no click, click sound when shook) seamed to be to long for the reg. I didn't want to risk damageing the reg so I removed it and put stock nipple back in. It filled fine and worked good for a few fills then started leaking again. I took it a part and same thing the o-ring was unseated and sticking out of the bottom of the nipple. Has anyone else had this problem and if so how did you fix it? Also I was wondering what other brand would work? The other nipple I had (I think it was made by 32degrees), had the o-ring set into a grove about 1/4 inch up the pin unlike the PE one that just sat on the bottome of the pin on a flange. The other one seemed like a better design.